The freeze drying process is used in the case of thermally sensitive goods such as e.g. pharmaceutical and biochemical products, foodstuffs etc, wherein the material to be dried is first frozen, ice which has crystallized out is sublimated out of the material under vacuum and reprecipitated as ice on condensers. For this purpose, the pressure, the temperature and further parameters of the drying process are controlled and monitored according to a product-specific sublimation pressure curve in order to achieve reproducible drying results. The energy required for the sublimation is generally supplied by heating.
Freeze drying installations are in many cases arranged for batch operation and consist predominantly of a drying chamber and a condenser chamber connected thereto via a closable opening, wherein the material to be dried is contained in a number of drying vessels, flasks, ampoules or even dishes, which are placed onto a standing surface within a drying chamber in order for drying to be carried out. A number of such standing surface are disposed one above the other in the drying chamber in a frame so that they can be displaced vertically in a spaced-apart manner. Since, during a drying process and depending on the size of the freeze drying installation, a large number of drying vessels each containing a certain quantity of material to be dried have to be inserted into the drying chamber and then removed after the drying process is completed, it is usual to use devices which operate in an automated manner for the loading and also for the unloading of the drying vessels, wherein even when ordering an installation it is currently necessary to establish whether loading and/or unloading will be carried out by hand or by means of appropriate devices operating in an automated manner. Retrofitting of a freeze drying installation which is to be loaded and/or unloaded manually to allow an integrated automated process is currently not possible or is possible only with considerable outlay.
Considering the temperature sensitivity of the material to be dried, but especially owing to the necessity of providing conditions which are aseptically problem-free for all installation components which come into contact with the material to be dried, particular attention must be given in the design of a loading and unloading device as to how the configuration and manner of operation thereof are achieved in terms of achieving asepsis.
From the document DE 103 07 571 A1 a loading and unloading device for a freeze drying installation is known, wherein on the outside in front of the loading and unloading opening of a drying chamber, a horizontally movable slide intended for loading purposes and a carriage, which is intended for unloading purposes and is similarly moveable horizontally into the chamber, are provided. The slide cooperates with a conveyor belt operated in a clocked manner, on which stand the drying vessels which are to be inserted into the chamber, and is characterized, amongst other things, by a strip which extends transversely with respect to the advancing direction of the loading process, which is intended to lie against the drying vessels and which can be driven on both lateral ends via a respective toothed rod drive. The carriage is formed by a frame which can be driven into the chamber separately by the slide via the unloading opening as far as the rear end opposite thereto, and in this case travels over the standing plate including the drying vessels standing thereon, wherein on both sides of the carriage a respective linkage system which can be wound up and which is suitable for transferring pulling and pushing forces is provided and is connected to a drive outside the chamber. The said frame which travels over the drying vessels is supported via rollers on the standing surface which is to be unloaded and which has lateral partitions. By means of a transversely extending structure which can be lowered automatically by the frame upon reaching a contact position at the said rear end, an entrainment effect on the drying vessels standing on the standing surface is produced so that the unloading process is initiated by actuation of the two linkage systems.
Almost all the components of this known loading and unloading device, including the said drives, are located outside the drying chamber so that there is a not inconsiderable requirement for space in front of the drying chamber. Separate systems for both loading and unloading are provided which are formed in mechanically entirely different ways and which are each of a relatively complicated construction and are therefore formed such that in association therewith they are prone to collecting dirt so that they are consequently troublesome to clean. In particular, the achievement of a condition which is sufficiently aseptic for use in, and in front of, a freeze drying installation is in any case rendered more difficult. The results of this are also found, amongst other places, in the said linkage systems which, in the same manner as the carriage, are guided in a plane above the standing surface to be unloaded, so that at this location abrasion is unavoidably produced which falls onto the standing surface. The results of this are also found in the mechanical system which effects the automatic lowering of the structure intended to exert an entrainment effect on the drying vessels standing on the standing surface. The fact that the standing surfaces used are provided with lateral partitions is also to be regarded as disadvantageous in terms of asepsis if it is considered that the carriage is supported via rollers which lie in the edge region of the standing surface and also unavoidably produce abrasion.
A comparable loading and unloading device for a freeze drying installation is known from the document WO 2005/121671. For the purpose of loading the standing plate, which is located in a loading position in front of a slit, intended for loading and unloading purposes, in the housing wall of the drying chamber, a slide is provided in that case and can move through the slot into and out of the drying chamber. Unloading is achieved by a conveyor strip which can travel along lateral guides extending in parallel with the edges of the standing plate, which conveyor strip can additionally pivot about its longitudinal axis and specifically between an insertion position intended for travel over the drying vessels standing on the standing plate, and an exit position to push the drying vessels out. The conveyor strip is driven during insertion into the drying chamber, during exit out of the drying chamber and also during pivoting about its longitudinal axis between the said positions by virtue of a traction means connected to the ends of the conveyor strip, with the cooperation of drives disposed outside the drying chamber and connected to the ends of the conveyor strip. The difficulties already described above concerning the achievement and maintenance of aseptic conditions arise to the same degree in this case. The slide also requires a not inconsiderable amount of space in front of the said slot.
Another loading and unloading device for a freeze drying installation is known from the document DE 60 2004 003 692 T2, which is characterized by guides extending into a chamber on both sides of a set-down surface, on each of which guides a carriage is disposed, wherein the two carriages are connected by a rod which is disposed, with pivot levers interposed, so as to be pivotable about an axis extending perpendicular to the guides between a lower position fulfilling a stop function while the vessels standing on the set-down surface are being pushed in, and an upper position permitting travel over the vessels and fulfilling an ejection function. The rod connecting the carriages is supported in its lower position via wheels which roll on the set-down surface. In front of an inlet opening outside the chamber is located a bar-like pusher mechanism which is arranged to push the vessels into the chamber. Belt drives are used to drive the carriages including the pivot mechanism of the said rod. Difficulties associated with the production of aseptic conditions also arise in the case of this device owing to the way the said rod is supported and the constructional formation and arrangement of the assemblies moveably disposed inside the chamber. In addition to unavoidable abrasion, there is the risk of the ingress of dirt from the environment, and there are the structurally complicated conditions also found with this loading and unloading device, which make cleaning difficult.